| Message ID | 349a25ddce02d55cf5a321f27133cae1f34f1962.camel@iris-sensing.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | pwm: imx-tpm: Use correct MODULO value for EPWM mode | expand |
On Wed, Oct 23, 2024 at 12:33:53PM +0000, Erik Schumacher wrote: > The modulo register defines the period of the edge-aligned PWM mode > (which is the only mode implemented). The reference manual states: > "The EPWM period is determined by (MOD + 0001h) ..." So the value that > is written to the MOD register must therefore be one less than the > calculated period length. > A correct MODULO value is particularly relevant if the PWM has to output > a high frequency due to a low period value. > This is bug fix, add fix tag and cc stable Frank > Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com> > --- > drivers/pwm/pwm-imx-tpm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c > index 96ea343856f0..a05b66ffe208 100644 > --- a/drivers/pwm/pwm-imx-tpm.c > +++ b/drivers/pwm/pwm-imx-tpm.c > @@ -106,7 +106,7 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip, > p->prescale = prescale; > > period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale; > - p->mod = period_count; > + p->mod = period_count - 1; > > /* calculate real period HW can support */ > tmp = (u64)period_count << prescale; > -- > 2.47.0 >
Am Mittwoch, dem 23.10.2024 um 11:35 -0400 schrieb Frank Li: > On Wed, Oct 23, 2024 at 12:33:53PM +0000, Erik Schumacher wrote: > > The modulo register defines the period of the edge-aligned PWM mode > > (which is the only mode implemented). The reference manual states: > > "The EPWM period is determined by (MOD + 0001h) ..." So the value that > > is written to the MOD register must therefore be one less than the > > calculated period length. > > A correct MODULO value is particularly relevant if the PWM has to output > > a high frequency due to a low period value. > > > This is bug fix, add fix tag and cc stable > > Frank That's true. I will do a v2 with these tags. Thank you! Erik >
diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c index 96ea343856f0..a05b66ffe208 100644 --- a/drivers/pwm/pwm-imx-tpm.c +++ b/drivers/pwm/pwm-imx-tpm.c @@ -106,7 +106,7 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip, p->prescale = prescale; period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale; - p->mod = period_count; + p->mod = period_count - 1; /* calculate real period HW can support */ tmp = (u64)period_count << prescale;
The modulo register defines the period of the edge-aligned PWM mode (which is the only mode implemented). The reference manual states: "The EPWM period is determined by (MOD + 0001h) ..." So the value that is written to the MOD register must therefore be one less than the calculated period length. A correct MODULO value is particularly relevant if the PWM has to output a high frequency due to a low period value. Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com> --- drivers/pwm/pwm-imx-tpm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)